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Diffusion Lab: Pumpkin

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Jerrilyn Gumila

on 4 November 2013

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Transcript of Diffusion Lab: Pumpkin

Diffusion & Osmosis Lab

Control(s): The distilled water & weight of pumpkin
Independent: Different water solutions
Dependent: The diffusion rate of the pumpkin
How does the amount of sucrose affect the final mass of the pumpkin after diffusion & osmosis?
If the concentration of glucose is higher, then the change in mass is greater.
Safety Considerations
The order we believe the water molarity goes in is:
1.0 =
0.8 =
0.6 =
0.4 =
0.2 =
0 =
After the experiment ended we found that there was one major error we made that could have interfered with the results we had. One major error being not removing the pumpkin skin. This could have messed with our results not letting diffusion to fully occur.
Our group hypothesized that after the pumpkin sat in the different sucrose solutions, the one that gained the most mass would have been the one sitting in the solution that had 1.0.
Cell Membrane= cell's interface w/ its surroundings
Must function as a barrier
Keeps together enzymes,
DNA, and metabolic pathways
Also functions as a gateway: waste products are
discharged through it and essential materials enter through it(oxygen)
Background cont.
Pumpkin (vegetable)
7 beakers
1 graduated cylinder
1 razor
1 Metal knife
100ml of distilled water
100ml of each colored Sucrose solution
Paper napkin
Plastic film cover
Scale (in grams)
1) Label the cups with the concentrations of sucrose that will be used.
2) With the cutting knife, cut 7 equally-weighted pieces of pumpkin. Use a scale & be sure to remove the skin!
If pieces cannot be weighed immediately, place in a cup with plastic wrap over to preserve water content. If not done, this will cause an error in the results from evaporation.
3) Record the weight of the pumpkin slices and the temperature of the area that the experiment is being conducted in.
4) Place each piece into 7 different cups, with each cup labeled for each concentration of solution (0.0, 0.2, 0.4, 0.6, 0.8, 1.0, and distilled water)
5) Pour 100 mL of of the appropriate solutions in the cups & cover each with plastic wrap.
Plastic wrap protects the fruit/vegetable & the solution from losing water, which if happened, would cause an error in the results because of evaporation.
Semipermeable: Membrane that allows some molecules to pass through while blocking the passage
Diffusion: Movement of molecules from higher concentration -> lower concentration
Osmosis: Diffusion of water molecules across a semipermeable membrane
Study the effects of osmosis and diffusion using different solutions
How water acts in different situations
Understand the concept of molarity and its association to osmosis

Works Cited
Campbell, Neil A., Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, and Peter V. Minorsky. AP Edition Biology Seventh Edition. New York: Benjamin/Cummings, 2008. Print.
6) Allow the solutions to sit overnight to allow the diffusion process to occur between the different solutions.
7) Remove the pumpkin pieces from their solutions & blot them with a paper towel to remove the excess solution from the pieces. Weigh the pieces on a scale
If they cannot be weighed immediately, repeat only the bullet point of Step 2.
8) Record the final mass of each slice appropriately.
9) Calculate the percent change in mass; this will give the amount of sugar/water lost/gained of the appropriate pieces of pumpkin.
10) Graph the percent change & find where line hits 0 on x-axis
This is the equilibrium point (no gain/loss of water in pumpkin cells)
Clean cups/beakers; could have dangerous chemicals, also affecting results
Keep hands away from face until cleaned
11) Record molarity at equilibrium and
label C
, convert room temperature from Celsius to K (Kelvins) &
label as T
, use
1 as i
, &
0.0831 as R
(pressure constant)
12) Use formula ~solute potential= - iCRT
13) Use ~solute potential + pressure potential* = water potential
*** 0.0831
The difference in solute & pressure predicts the direction in which water will diffuse through living plants
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